On the basis of traditional methods for preparing lithium manganate with electrolytic manganese dioxide, in order to solve the circulation property of lithium manganate prepared with electrolytic manganese dioxide, international mainstream manufactures and firms are inclined to the trimanganese tetroxide material which is specially designed for lithium ion battery, and new requirements for physical and chemical indexes of the trimanganese tetroxide is put forward. Main indexes are shown as follows:
D50 is 10˜12 μm, or 14˜16 μm.
BET specific surface area is <1 m2/g.
Fe content is <10 ppm.
Heavy metal content is <3 ppm.
The particle size distribution is narrow, the particle is spherical, and the structure is pure phase crystal structure.
A method for preparing Mn3O4 by adding aqueous ammonia into MnSO4/H2O solution is disclosed in CN1814551A. In this method, the oxidation rate of divalent manganese and the recovery rate of manganese are largely increased, but it can not be ensured to obtain Mn3O4 with pure phase structure. In the meanwhile, because the physical indexes such as particle size distribution, specific surface area and so on, are not studied and are not technically controlled during the process for preparing Mn3O4, the obtained Mn3O4 is not suitable for preparing lithium manganate materials.
A method for preparing Mn3O4 by oxidizing the system of MnSO4/H2O/NH4OH with air is disclosed in CN101898796A. In this method, tap density is increased, but particle size distribution and particle shape of Mn3O4 are not controlled, so the specific surface area of the product is relatively large and impurities of Fe and heavy metals content is relatively high, which leads to a certain gap between properties of the product and the international mainstream clients' requirements. In the meanwhile, research for the doping of aluminum which can improve the circulation property of battery is not concerned in the patent.